Go for it. And remind them that Santa needs a change every now and then - but if anyone doesn't want their stocking (or believe in Santa) then you would be very happy to send everything back to santa unopened! And by complete coincidence I think you'll find that everybody is more than happy to agree that santa does exist and they do believe 
It is great to have them to open in the mornings - the anticipation of finding them on your bed or on the floor, being able to open them early in the morning and eating chocolate coins before breakfast, the fun showing the stuff to your parents (or opening on the bed with them).
My sister hit upon the ruse of leaving a stocking out for her dolls too - first year santa left a few extra sweets for them, so she left one out every year after that. One year, she found a massive bag that she folded up very small - mum has subsequently said that when she and dad were filling them up (crazy late at night as we'd had guests and she hadn't even started wrapping stuff beforehand) that they opened this little bag expecting it to be the normal size and it just kept on getting bigger and bigger and bigger - and as they were so tired and pissed it gave them such a bad laughing fit (you know the sort - where you just can't stop) that it was the only time they worried that they would wake us up.
I often put stuff that the dc need in their stocking that they would be getting anyway, as well as fun stuff, so it doesn't end up costing too much in 'present' money.
There's always a satsuma and bag of chocolate coins at the very bottom.
There's usually a new vest, pair of pants, pair of socks and nice t-shirt or shirt in it - conveniently ready to wear for christmas day itself (no faffing around finding stuff to wear when you're trying to organise cooking the turkey or getting presents opened). Rest of the pack of pants, socks etc usually ends up wrapped up as tree presents from santa.
There's a new toothbrush - albeit a fun one. and a bottle of bubble bath (double wrapped in a plastic bag first just in case of spillages!)
Notebook and either colouring pens and/or pencils/pens. Little sets of cute felt tips cost less than a pound in Tesco
Lego shops usually sell a charity little lego kit for a couple of pounds or a lego christmas kit (bought one today in fact that cost £3 of santa in a sleigh) - they are in a bag rather than a box, so a good stocking present for being crinkly and funny shaped.
sometimes a christmas special comic - if you roll it up it goes down the leg well. And they usually have a couple of bits of plastic tat toys on to entertain.
a card game and/or small book
Toy car or two (or maybe a toy plane or motor bike) - just the little ones that cost about a pound in the supermarket
I have learnt the hard way not to include anything that you do not want opened and spilt on the bed or carpet - no playdoh, scooby slime, alien slime etc (had you guessed I have boys!)
a new comb - they always go missing!
Finally it's always topped off by a cuddly toy, unwrapped, peeking out of the top of the stocking and watching you waiting for you to open the stocking!